Large dose ribavirin formulations

ABSTRACT

The present invention is related to pharmaceutical dosage forms of ribavirin which are designed to increase patient compliance to a ribavirin therapy. Examples of such dosage forms include 400 mg to 600 mg tablets. These dosage forms are bioequivalent to multiple doses of tablets containing small amounts of ribavirin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Application of U.S. Ser. No. 11/201,311 filed, Aug. 11, 2005, which claims priority to U.S. Provisional Application No. 60/619,013, filed Oct. 18, 2004. The disclosure of the prior applications is hereby incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is generally directed to large dosage formulations of ribavirin.

2. Background of the Invention

Ribavirin (1-β-D-ribofuranosyl-1H-1,2,4-triazole-3-carbamide) is a broad-spectrum antiviral nucleoside analog. It is available as a capsule and tablet in both the brand and generic form in 200 mg strength. The Food and Drug Administration has approved ribavirin in combination with interferon alfa-2a or interferon alfa-2b for the treatment of hepatitis-C. Over 170 million people worldwide are chronically infected with the hepatitis-C virus (HCV). Ribavirin is available as a 200 mg tablet by Roche Laboratories under the brand COPEGUS™ and as a 200 mg capsule by Schering-Plough under the brand REBETOL™.

The most common doses prescribed for patients are 800 mg, 1000 mg, and 1200 mg per day in divided doses for both the capsule and tablet dosage forms. These dosing regimens have the patient taking up to 6 capsules or tablets per day. Ribavirin is not often given by itself; it is generally a component of a multi-drug regimen (“drug cocktail”). Therefore patients taking ribavirin have to take a large number of drugs, not in the least of which is 4 to 6 capsules or tablets of ribavirin. Not surprisingly, lack of patient compliance is a significant issue.

HCV has about a 50 percent cure rate depending upon a patient's genotype. Everything must be done to ensure patient compliance to the therapy that lasts 6 to 12 months. If dosing is more convenient for the patient, then it follows that the patient will more likely comply with the dosing regimen for the duration of therapy, which has been proven to improve patient outcomes.

Therefore, there exists a long-felt need to make the dosing of ribavirin more convenient for the patient and increase patient compliance.

From a convenience standpoint, one logical approach to the formulator would be to formulate a modified or sustained release form of ribavirin, which would result in fewer capsules or tablets taken daily. However, in the case of ribavirin, such an approach would not be successful. The pharmacokinetics of ribavirin are controlled by the rate of elimination, not absorption. Therefore, modifying the rate of release or absorption of ribavirin would not likely affect the efficacy of ribavirin. In other words, sustained release formulations of ribavirin are likely not a solution in this instance.

The present inventors have concluded that in the case of ribavirin, the optimal dosage regimen is two times a day. The inventors then strove to formulate dosage forms with a twice-a-day dosing regimen which would increase patient compliance while maintaining bioactivity similar to lower (e.g., 200 mg) dose formulations.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to an oral dosage form of ribavirin, preferably a capsule, tablet or caplet, in 400 mg to 600 mg dosage strengths.

Another aspect of the present invention is directed to dosage forms of ribavirin that increase patient compliance.

Another aspect of the invention is directed to dosage forms of ribavirin that satisfy a long-felt need in the market for ribavirin dosage forms.

Another aspect of the invention is directed to dosage forms of ribavirin comprising high amounts of ribavirin, relative to commercially available formulations, which have similar bioactivities to the commercially available formulations.

A further aspect of the invention is directed to a dosage form comprising 400 mg of ribavirin.

A further aspect of the invention is directed to a dosage form comprising 600 mg of ribavirin.

Another aspect of the invention is directed to dosage forms of ribavirin in unit dose packaging, such as blister packaging.

Other aspects, features, and advantages of the invention will become apparent from the following detailed description and figure.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 shows mean in vivo ribavirin plasma levels of three formulations in a bioavailability study of 36 subjects. COPEGUS™ 3×200 mg means that the brand name ribavirin product was given in a dosage of three 200 mg tablets. RIBASPHERE™ 3×200 mg means that the generic ribavirin product was given in a dosage of three 200 mg tablets. RIBASPHERE™ 1×600 mg means that a ribavirin product according to the invention was given at a dosage of one 600 mg tablet.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, the term “dosage form” includes capsules and tablets, and the term “tablet” includes both tablets and caplets. The dosage form of the invention is preferably a tablet, and more preferably a caplet.

The present application describes the development of dosage forms of ribavirin in 400 mg to 600 mg dosage strengths. In order to test bioequivalency, subjects were dosed with 600 mg tablets. A corresponding number of COPEGUS™ and generic 200 mg tablets were used as a comparison. FIG. 1 shows that the in vivo dissolution profile of a 600 mg tablet according to the present invention is similar to the dissolution profile of three 200 mg COPEGUS™ tablets. In other words, the higher strength tablets according to the present invention are bioequivalent to the brand name product. Further, the preferred caplet shape makes it easier for the patient to swallow and the tablets are acceptable as not being too large in size.

The patient now only has to take one tablet twice a day instead of 2 or 3 tablets twice a day. This new, more convenient dose keeps patients more compliant to their drug regimen, which improves outcomes. To this point, no drug manufacturer has manufactured a large dosage form of ribavirin. There is a clear and long-felt need in the industry for such a product.

The dosage forms of the present invention can be made of the same general ingredients (e.g., binders, fillers, disintegrants, lubricants and the like) and in the same manner as commercially available ribavirin tablets. In one embodiment of the present invention, a tablet comprises one or more of the following inactive ingredients: microcrystalline cellulose; lactose; crosscarmellose sodium; Povidone; and magnesium stearate. In another embodiment of the present invention, the tablet is coated and the coating preferably comprises: Opandry II Blue (which in turn comprises polyvinyl alcohol-part hydrolyzed, titanium dioxide, macrogel/PEG 3350, talc, and FD&C blue #2/indigo carmine aluminum lake); and carnauba wax.

One example of the formulation of a 400 mg ribavirin tablet in accordance with the present invention is shown in Table I:

TABLE I Component Weight/tablet (mg) Ingredient Active 400.0 Ribavirin Binder/disintegrant 84.4 Microcrystalline cellulose Filler 30.0 Lactose monohydrate Disintegrant 25.4 Crosscarmellose sodium Binder 6.0 Povidone Lubricant 4.2 Magnesium stearate Water (removed during Purified water drying)

One example of the formulation of a 600 mg ribavirin tablet in accordance with the present invention is shown in Table II:

TABLE II Component Weight/tablet (mg) Ingredient Active 600.0 Ribavirin Binder/disintegrant 126.6 Microcrystalline cellulose Filler 45.0 Lactose monohydrate Disintegrant 38.1 Crosscarmellose sodium Binder 9.0 Povidone Lubricant 6.3 Magnesium stearate Water (removed during Purified water drying)

One embodiment of a 400 mg tablet according to the present invention has hardness of from about 10.27 kp to about 12.88 kp, preferably 11.18 kp. Another embodiment of a 400 mg tablet according to the present invention has a tablet weight of from about 0.5470 g to about 0.5535 g, preferably 0.5494 g. Another embodiment of a 400 mg tablet according to the present invention has a tablet thickness of from about 4.86 mm to about 4.91 mm, preferably 4.89 mm. Another embodiment of a 400 mg tablet according to the present invention has a tablet friability of from about 0.23% to about 0.26%, preferably 0.25%. Another embodiment of a 400 mg tablet according to the present invention has a compression force of from about 13.5 kN to about 16.6 kN, preferably 14.9 kN.

One embodiment of a 600 mg tablet according to the present invention has hardness of from about 10.64 kp to about 12.58 kp, preferably 11.60 kp. Another embodiment of a 600 mg tablet according to the present invention has a tablet weight of from about 0.8174 g to about 0.8357 g, preferably 0.8272 g. Another embodiment of a 600 mg tablet according to the present invention has a tablet thickness of from about 6.38 mm to about 6.41 mm, preferably 6.39 mm. Another embodiment of a 600 mg tablet according to the present invention has a tablet friability of from about 0.23% to about 0.33%, preferably 0.29%. Another embodiment of a 600 mg tablet according to the present invention has a compression force of from about 12.2 kN to about 14.2 kN, preferably 13.1 kN.

Compression and film coating of the tablets according to the present invention may be accomplished by standard industry means. For example, tablets may be compressed using a 16-station Manesty Beta press using capsule shaped tooling. The tablets may be film coated using a 24-inch Accela Cota pan equipped with 2 spray guns with a target air flow of about 300 cfm and an exhaust temperature of between about 50° C. to 55° C. The pan speed and the target spray rate can be adjusted to suit the particular tablet being coated. As indicated previously, in one embodiment, Opandry II Blue coating is used. Any suitable coating can be used in accordance with the present invention.

The tablets according to the present invention may be of any color, preferably blue, more preferably light-blue, medium blue, or dark blue. The tablets can also be of any shape, preferably flat and oval-shaped. The tablets may be dispensed in any form including blister packs and HDPE bottles, which may or may not include child-resistant closures with induction seals. Any number of tablets may be included in a unit dose package, such as a blister pack, including 2, 4, 6, 8, 10, 12, 16, 20, 24, 48 or 56.

Example 1 A Comparative Bioavailability Study of Ribavirin Tablets Under Fasting Conditions

Ribavirin plasma levels under fasting conditions, produced after administration of (a) three Ribasphere® 200 mg tablets and (b) one Ribasphere® 600 mg tablet were compared with those produced after administration of three Copegus® 200 mg tablets.

The 200 mg and 600 mg Ribasphere® tablets are manufactured by Three Rivers Pharmaceuticals, LLC; ribavirin tablets. The Copegus® 200 mg tablets were manufactured by Roche®.

The study was administered and coordinated by Bioanalytical Systems, Inc. (BASi), Clinical Research Unit (CRU), Baltimore, Md. The clinical portion of the study was conducted by Gateway Medical Research, Inc. The laboratory analysis of plasma samples and statistical analysis of the concentration-time data was conducted at BASi CRU. Forty-one healthy female subjects were enrolled in this three-treatment crossover study. Blood samples from all subjects who completed the study were analyzed. The subjects received a single oral dose of ribavirin 600 mg on three occasions separated by a washout period of three weeks. Blood samples were obtained at 15 time points from predose (0-hour) until 72 hours post-dose. The plasma samples were analyzed by a specific validated LC/MS/MS method to determine ribavirin concentrations.

The ribavirin concentrations were used to calculate the area under the concentration-time curve to the last non-zero time point (AUC_(0-T)), elimination rate constant (K_(el)), half-life (T_(1/2)) and AUC 0-Infinity (AUC_(0-Inf)). The actual times of sample collections were used in the calculations. The maximum drug concentration (C_(max)) and the time to maximum drug concentration (T_(max)) were also reported. The arithmetic mean and standard deviation were calculated for each parameter and for the ribavirin concentrations at each time point. The geometric means were calculated for AUC_(0-T), AUC_(0-Inf) and C_(max). All parameters were analyzed by an analysis of variance (ANOVA) using the general linear model (GLM). The ANOVA included effects for sequence of drug treatment, subject nested within sequence, period and drug treatment in the statistical model. The F-test was employed to determine the statistical significance of each effect in the model. The sequence effect was tested using the subject (sequence) mean square as the error term (α=0.10), while the other effects were tested against the residual error (α=0.05). The power of the study to detect a 20% difference in parameter means as statistically significant under a 2-tailed test at the 5% level of the t-distribution was calculated for each pharmacokinetic metric.

The test and reference means (and geometric means), and the ratios of means, test/reference, were reported using the least squares means from the ANOVA. An assessment of bioequivalence was conducted for the test versus reference product comparison of AUC and C_(max) after log transformation using 90% confidence intervals for the differences in treatment means. These were transformed into 90% confidence intervals for the ratios of the means (test/reference) by exponentiation. The products were considered bioequivalent if the 90% confidence intervals about the ratios of means for AUC and C_(max) were contained within the limits 0.80 to 1.25.

Of the 41 subjects enrolled into the study, 36 subjects completed all study periods. The plasma samples were analyzed for all completed subjects. Several of the subjects experienced at least one adverse event. Ribavirin was measured in the predose sample of period I for one subject, in the predose sample of period II for nine subjects, and in the predose sample of period III for 21 subjects. The predose concentration detected was less than 5% of the individual C_(max) value for all but four subjects.

The sampling schedule for ribavirin proved to be suitable for estimation of T_(max) in this bioavailability study. The first post-dose sample was not the maximum observed concentration after 94 of the 96 doses. Two post-dose samples were obtained before the average time of the maximum concentration.

The sampling schedule was truncated at 72 hours post-dose for this long half-life drug, eighty percent of AUC_(0-Inf) was not typically measured by AUC_(0-T). Therefore, in the results that follow, emphasis should be placed on AUC_(0-T), since AUC_(0-Inf) was not generally well estimated.

There were no statistically significant (α=0.05) differences between the formulations for AUC_(0-T) or C_(max), while there was a statistically significant formulation difference observed for AUC_(0-Inf). There were no statistically significant sequence effects (α=0.10) for any AUC or C_(max) parameter, and there was no statistically significant period effects (α=0.05) for C_(max).

The results show that three ribavirin Ribasphere® 200 mg tablets is bioequivalent to three Copegus® 200 mg tablets when both were administered under fasting conditions. Similarly, the ribavirin Ribasphere® 600 mg is bioequivalent to three ribavirin Copegus® 200 mg tablets when administered under fasting conditions. For AUC_(0-T), AUC_(0-Inf) and C_(max), the 90% confidence intervals were within the 0.80 to 1.25 bioequivalence limits for both comparisons.

TABLE III Ribavirin Ratio of Means 90% Confidence (n-32) (test/reference) Interval Ribasphere ® 3 × 200 mg vs. Copegus ® 3 × 200 mg AUC_(0-T) 0.95 0.89; 1.00 AUC_(0-Inf) 0.92 0.87; 0.97 C_(max) 0.96 0.89; 1.03 Ribasphere ® 1 × 600 mg vs. Copegus ® 3 × 200 mg AUC_(0-T) 0.98 0.92; 1.04 AUC_(0-Inf) 1.01 0.96; 1.07 C_(max) 0.97 0.90; 1.05 Based on least squares after logarithmic transformation of the data

TABLE IV RIBAVIRIN PLASMA CONCENTRATIONS (ng/ml) Test1: Ribasphere Test 2: Ribasphere Ref: Copegus Time 3 × 200 mg 1 × 600 mg 3 × 200 mg Ratio Ratio Ratio (Hours) N Mean ± Std Dev N Mean ± Std Dev N Mean ± Std Dev Test 1/Test 2 Test/Ref Test 2/Ref Significance 0 32 9.319 ± 15.54 32 7.472 ± 13.36 32 8.713 ± 16.63 1.25 1.07 0.86 0.5 32 435.0 ± 231.6 32 425.0 ± 255.1 32 348.5 ± 198.7 1.02 1.25 1.22 N.S. 1 32 811.5 ± 312.7 32 806.9 ± 267.8 32 825.0 ± 328.2 1.01 0.98 0.98 N.S. 1.5 32 859.2 ± 274.8 32 889.3 ± 317.9 32 965.6 ± 401.5 0.97 0.89 0.92 N.S. 2 32 794.5 ± 302.5 32 817.0 ± 272.7 32 907.2 ± 390.6 0.97 0.88 0.90 N.S. 3 32 648.3 ± 274.8 32 642.5 ± 221.2 32 706.0 ± 321.4 1.01 0.92 0.91 N.S. 4 32 528.8 ± 186.5 32 533.0 ± 169.7 32 552.7 ± 223.4 0.99 0.96 0.96 N.S. 6 32 419.5 ± 141.4 32 425.3 ± 151.1 32 422.1 ± 160.3 0.99 0.99 1.01 N.S. 8 32 320.1 ± 89.66 32 340.8 ± 117.8 32 330.9 ± 105.1 0.94 0.97 1.03 N.S. 12 32 246.5 ± 75.29 32 251.2 ± 81.48 32 260.2 ± 92.76 0.98 0.95 0.97 N.S. 16 32 230.4 ± 77.53 32 234.2 ± 68.48 32 240.6 ± 78.96 0.98 0.9′6 0.97 N.S. 24 32 211.2 ± 61.13 32 212.4 ± 70.36 32 214.9 ± 70.82 0.99 0.98 0.99 N.S. 36 31 158.6 ± 55.79 32 163.1 ± 55.60 30 171.4 ± 54.10 0.97 0.92 0.95 N.S. 48 31 136.0 ± 44.73 32 146.6 ± 42.12 32 152.7 ± 53.24 0.93 0.89+ 0.96 p < 0.05 72 32 106.0 ± 43.65 32 110.5 ± 35.09 32 111.4 ± 37.46 0.96 0.95 0.99 N.S.

TABLE V PHARMACOKINETIC PARAMETERS FOR PLASMA RIBAVIRIN Test1: Ribasphere Test 2: Ribasphere Ref: Copegus 3 × 200 mg 1 × 600 mg 3 × 200 mg Ratio Ratio Ratio Parameter N Mean ± Std Dev N Mean ± Std Dev N Mean ± Std Dev Test 1/Test 2 Test 1/Ref Test 2/Ref Ln AUC_(0-T) 32 9.5776 ± 0.2769 32 9.6097 ± 0.2683 32 9.6302 ± 0.3008 0.97 0.95 0.98 Geometric Mean 14438 14909 15218 Ln AUC_(0-Inf) 32 9.9712 ± 0.3326 31 10.0599 ± 0.3161  30 10.0579 ± 0.3264  0.92 0.92 1.00 Geometric Mean 21401 23387 23339 Ln C_(max) 32 6.8292 ± 0.3181 32 6.8435 ± 0.2937 32 6.8703 ± 0.3793 0.99 0.96 0.97 Geometric Mean    924.4    937.8    963.2 AUC_(0-T) (ng · h/ml) 32 15002 ± 4413  32 15447 ± 4288  32 15902 ± 4864  0.97 0.94 0.97 AUC_(0-Inf) (ng · h/ml) 32 22645 ± 8290  31 24570 ± 8091  30 24576 ± 8255  0.92 0.92 1.00 C_(max) (ng/ml) 32 971.1 ± 314.4 32 979.9 ± 315.9 32  1033 ± 402.6 0.99 0.94 0.95 T_(max) (h) 32  1.501 ± 0.5680 32  1.455 ± 0.5605 32  1.517 ± 0.5301 1.03 0.99 0.96 K_(el) (1/h) 32  0.01531 ± 0.003645 31  0.01407 ± 0.003963 30  0.01484 ± 0.003230 1.09 1.03 0.95 T_(1/2) (h) 32 47.69 ± 10.71 31 53.61 ± 16.65 30 49.22 ± 12.41 0.89 0.97 1.09

TABLE VI PHARMACOKINETIC PARAMETERS FOR PLASMA RIBAVIRIN Test 1 Ribasphere Test 2 Ribasphere Reference Copegus Ratio Ratio Ratio Parameter 3 × 200 mg 1 × 600 mg 3 × 200 mg Test I/Test 2 Test 1/Ref Test 2/Ref Significance Ln AUC_(0-T)  9.5829 ± 0.02500  9.6160 ± 0.02502  9.6380 ± 0.02497 0.97 0.95 0.98 N.S. Geometric Mean (14515) (15003) (15337) Ln AUC_(0-Inf) 19.9716 ± 0.02232 10.0689 ± 0.02286 10.0594 ± 0.02324 0.91+ 0.92+ 1.01 p < 0.05 Geometric Mean (21410) (23597) (23374) Ln C_(max)  6.8316 ± 0.03122  6.8451 ± 0.03125  6.8737 ± 0.03119 0.99 0.96 0.97 N.S. Geometric Mean    (926.7)    (939.2)    (966.5) AUC_(0-T) (ng · h/ml) 15108 ± 414.3  15566 ± 414.7  16051 t ± 413.9 0.97 0.94 0.97 N.S. AUC_(0-Inf) (ng · h/ml) 22722 ± 625.5  24820 ± 640.9  24687 ± 651.4  0.92 0.92 1.01 p < 0.05 C_(max) (ng/ml) 974.6 ± 34.31 983.3 ± 34.34  1038 ± 34.28 0.99 0.94 0.95 N.S. T_(max) (h)  1.487 ± 0.09425  1.457 ± 0.09435  1.511 ± 0.09416 1.02 0.98 0.96 N.S. K_(el) (1/h)  0.01542 ± 0.000410  0.01393 ± 0.000420  0.01474 ± 0.000427 1.11+ 1.05 0.95 p < 0.05 T_(1/2) (h) 47.29 ± 1.639 54.27 ± 1.679 49.74 ± 1.707 0.87+ 0.95 1.09 p < 0.05

TABLE VII PHARMACOKINETIC PARAMETERS FOR PLASMA RIBAVIRIN Contrast Measured Ratio Study Intrasubject 90% Confidence of Means Parameter (Test/Ref) Power C.V. (%) Interval Ribasphere 3 × 200 mg Ln AUC_(0-T) 0.97 >0.99 14.1 [0.91; 1.03] vs. Ribasphere Ln AUC_(0-Inf) 0.91 >0.99 12.6 [0.86; 0.96] 1 × 600 mg Ln C_(max) 0.99 >0.99 17.7 [0.92; 1.06] AUC_(0-T) (ng · h/ml) 0.97 >0.99 15.1 [0.91; 1.03] AUC_(0-Inf) (ng · h/ml) 0.92 >0.99 14.7 [0.86; 0.98] C_(max) (ng/ml) 0.99 0.98 19.4 [0.91; 1.07] Ribasphere 3 × 200 mg Ln AUC_(0-T) 0.95 >0.99 14.1 [0.89; 1.00] vs. Copegus 3 × 200 mg Ln AUC_(0-Inf) 0.92 >0.99 12.6 [0.87; 0.97] Ln C_(max) 0.96 >0.99 17.7 [0.89; 1.03] AUC_(0-T) (ng · h/ml) 0.94 >0.99 15.1 [0.88; 1.00] AUC_(0-Inf) (ng · h/ml) 0.92 >0.99 14.7 [0.86; 0.98] C_(max) (ng/ml) 0.94 0.99 19.4 [0.86; 1.02] Ribasphere 1 × 600 mg Ln AUC_(0-T) 0.98 >0.99 14.1 [0.92; 1.04] vs. Copegus 3 × 200 mg Ln AUC_(0-Inf) 1.01 >0.99 12.6 [0.96; 1.07] Ln C_(max) 0.97 >0.99 17.7 [0.90; 1.05] AUC_(0-T) (ng · h/ml) 0.97 >0.99 15.1 [0.91; 1.03] AUC_(0-Inf) (ng · b/ml) 1.01 >0.99 14.7 [0.94; 1.07] C_(max) (ng/ml) 0.95 0.99 19.4 [0.87; 1.02]

It is to be understood that while the invention has been described above using specific embodiments, the description and examples are intended to illustrate the structural and functional principles of the present invention and are not intended to limit the scope of the invention. On the contrary, the present invention is intended to encompass all modifications, alterations, and substitutions. 

1. A method for increasing patient compliance of a therapy comprising ribavirin, the method comprising administering a single pharmaceutical dosage form comprising 400 mg to 600 mg of ribavirin.
 2. The method of claim 1, wherein the dosage form comprises 400 mg of ribavirin and further comprises at least one excipient selected from the group consisting of microcrystalline cellulose, lactose monohydrate, crosscarmellose sodium, povidone and magnesium stearate.
 3. The method of claim 1, wherein the dosage form comprises 600 mg of ribavirin and further comprises at least one excipient selected from the group consisting of microcrystalline cellulose, lactose monohydrate, crosscarmellose sodium, povidone and magnesium stearate.
 4. A method for increasing patient compliance of a therapy comprising ribavirin, the method comprising administering, twice a day to a subject, exactly one dosage form comprising 400 mg to 600 mg of ribavirin.
 5. The method of claim 4, wherein the dosage form comprises 400 mg of ribavirin and further comprises at least one excipient selected from the group consisting of microcrystalline cellulose, lactose monohydrate, crosscarmellose sodium, povidone and magnesium stearate.
 6. The method of claim 4, wherein the dosage form is a 400 mg tablet which has at least one of the following characteristics: a tablet hardness of from about 10.27 kp to about 12.88 kp; a tablet weight of from about 0.5470 g to about 0.5535 g; a tablet thickness of from about 4.86 mm to about 4.91 mm; and a tablet friability of from about 0.23% to about 0.26%.
 7. The method of claim 4, wherein the dosage form comprises 600 mg of ribavirin and further comprises at least one excipient selected from the group consisting of microcrystalline cellulose, lactose monohydrate, crosscarmellose sodium, povidone and magnesium stearate.
 8. The method of claim 4, wherein the dosage form is a 600 mg tablet which has at least one of the following characteristics: a tablet hardness of from about 10.64 kp to about 12.58 kp; a tablet weight of from about 0.8174 g to about 0.8357 g; a tablet thickness of from about 6.38 mm to about 6.41 mm; and a tablet friability of from about 0.23% to about 0.33%.
 9. The method according to claim 4, wherein the dosage form is a tablet which is dispensed in HDPE bottles.
 10. The method according to claim 4, wherein the dosage form is a tablet which is dispensed in a unit dose package.
 11. The method according to claim 10, wherein the unit dose package is a blister pack containing 2, 4, 6, 8, 10, 12, 16, 20, 24, 48 or 56 tablets.
 12. A daily dosage regimen of ribavirin treatment comprising administering to a patient in need thereof exactly one dosage form of ribavirin and 8 hours to 16 hours later administering another one dosage form of ribavirin.
 13. The daily dosage regimen of claim 12, wherein the dosage form comprises 400 mg to 600 mg of ribavirin.
 14. The daily dosage regimen of claim 13, wherein the dosage form is a tablet which comprises 400 mg of ribavirin.
 15. The daily dosage regimen of claim 13, wherein the dosage form is a tablet which comprises 600 mg of ribavirin. 